1. Field of the Invention
The invention relates to the field of ultrasound imaging. More specifically, the invention relates to the field of signal processing in ultrasound systems which may employ Doppler.
2. Background Information
Various techniques and systems may be used to obtain images of the interior of a body and/or flow structures within a body. (A body is used herein to refer to various types of subjects, such humans, animals, non-living structures, etc., while flow structure as used herein may refer to a region of fluid flow such as occurring in veins, arteries, etc.) Some of these imaging techniques include magnetic resonance imaging (MRI), CT, and ultrasound. Among such techniques, ultrasound Doppler, which processes echoes (i.e., received signals based on transmitted signals), has provided relatively substantial convenience and cost efficiency, to both the equipment operator and the subject (body), compared to the X-ray, MRI and CT imaging techniques.
Continuous wave (CW) Doppler and pulsed wave (PW) Doppler are two examples of ultrasound Doppler imaging techniques often utilized in medical applications. CW Doppler is typically utilized to measure the velocity of blood or other fluid flow within a body. In applications wherein the velocity of the fluid flow may be relatively large, the modality of CW Doppler may be particularly useful, since CW Doppler, unlike PW Doppler, is generally not limited with respect to the magnitude of the maximum velocity that can be measured. As such, CW Doppler may be utilized, for example, to measure the velocity of blood in certain heart lesions, wherein the velocity of fluid flow may be relatively large (e.g., up to 7 m/s or more).